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      <title>讲一下数据库的ACID - 交互式测验</title>
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    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>讲一下数据库的ACID - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
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  {
    "question": "根据文档，数据库事务（Transaction）最核心的定义是什么？",
    "options": [
      "一个用于备份和恢复数据库的独立程序。",
      "一个由一个或多个SQL语句组成的逻辑工作单元，这些语句要么全部成功，要么全部失败。",
      "一组用于优化数据库查询性能的SQL语句。",
      "一个确保数据库物理存储安全的机制。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出，事务是一个逻辑工作单元，其关键特性是“要么全部成功，要么全部失败”，这正是原子性的体现，也是事务的核心概念。其他选项描述的是数据库管理的其他方面，如性能优化或备份恢复，而非事务本身。",
    "source": "文档中「什么是事务」部分",
    "hint": "思考一下事务作为一个“逻辑工作单元”的整体性特征。"
  },
  {
    "question": "在银行转账场景中，从账户A扣款后，系统在向账户B存款时发生故障。根据原子性（Atomicity）原则，数据库系统应该如何处理？",
    "options": [
      "暂停事务，等待系统恢复后再继续向账户B存款。",
      "回滚整个事务，撤销从账户A扣款的操作，使数据库恢复到事务开始前的状态。",
      "只提交从账户A扣款成功的操作，并记录存款失败的日志。",
      "强制完成向账户B存款的操作，以保证数据最终一致。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "原子性（Atomicity）的核心是“要么全部成功，要么全部失败”。如果事务中的任何一步失败，所有已执行的操作都必须被撤销（回滚），以保证数据不会处于一个不一致的“中间状态”。因此，正确的处理方式是回滚整个事务。",
    "source": "文档中「原子性（Atomicity）」部分",
    "hint": "原子性确保事务是一个不可分割的单元，没有中间状态。"
  },
  {
    "question": "数据库事务的持久性（Durability）特性主要保证了什么？",
    "options": [
      "事务的所有操作要么全部成功，要么全部失败。",
      "事务在执行期间不会被其他并发事务干扰。",
      "一旦事务被提交，其结果就是永久性的，即使系统发生断电或崩溃也不会丢失。",
      "事务执行前后，数据库都保持在有效的业务规则状态。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "持久性的核心在于“永久保存”。它通过将事务的变更写入非易失性存储（如硬盘上的日志文件）来确保，一旦系统通知用户事务已成功提交，那么这些变更就不会因后续的系统故障而丢失。其他选项分别描述的是原子性、隔离性和一致性。",
    "source": "文档中「持久性（Durability）」部分",
    "hint": "持久性关注的是事务提交后，数据的“存活”能力，即使面对系统故障。"
  },
  {
    "question": "哪个隔离级别（Isolation Level）能够防止“脏读”（读取其他事务未提交的变更），但仍可能出现“不可重复读”问题？",
    "options": [
      "读未提交 (Read Uncommitted)",
      "可重复读 (Repeatable Read)",
      "可序列化 (Serializable)",
      "读已提交 (Read Committed)"
    ],
    "correctAnswerIndex": 3,
    "explanation": "文档中描述，“读已提交 (Read Committed)”级别保证事务只能读取已提交事务的变更，从而防止了脏读。但是，由于在同个事务中多次读取数据时，其他事务可能已经提交了新的变更，导致两次读取结果不同，这正是“不可重复读”问题。",
    "source": "文档中「隔离性（Isolation）」->「3. 隔离级别」部分",
    "hint": "寻找一个介于最低和较高隔离级别之间的选项，它解决了一个问题，但留下了另一个。"
  },
  {
    "question": "根据文档，一致性（Consistency）在数据库事务中扮演的主要角色是什么？",
    "options": [
      "确保事务的执行不会违反数据库的任何预设约束（如主键、外键）和业务规则，使数据库从一个有效的状态转换到另一个有效的状态。",
      "确保事务日志被正确写入磁盘，以便在故障后恢复。",
      "确保多个用户同时访问数据时，他们看到的数据版本是一致的。",
      "确保事务可以被完整地回滚到开始前的状态。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "一致性是ACID中的“业务逻辑”层面的保证。它关注的是数据的有效性和正确性，确保事务操作始终遵守数据库定义的规则（如约束、触发器），从而维护了数据的完整性，使数据库从一个一致的状态转移到另一个一致的状态。",
    "source": "文档中「一致性（Consistency）」部分",
    "hint": "一致性关注的是数据是否满足预定义的规则和业务逻辑的正确性。"
  },
  {
    "question": "文档中提到的“写提前日志 (Write-Ahead Logging, WAL)”是一种关键技术，它主要用于实现哪个ACID特性？",
    "options": [
      "隔离性 (Isolation)",
      "一致性 (Consistency)",
      "持久性 (Durability)",
      "原子性 (Atomicity)"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档在持久性部分明确指出，写提前日志（WAL）是实现持久性的一种常用技术。它要求在数据变更写入数据库之前，必须先将描述这些变更的日志记录写入到稳定的存储中。这确保了即使系统崩溃，也可以通过日志来恢复已提交的事务。虽然WAL也辅助实现原子性（用于回滚），但其在保障数据不丢失方面的核心作用是实现持久性。",
    "source": "文档中「持久性（Durability）」->「2. 持久性的实现机制」部分",
    "hint": "这项技术的核心思想是在“写”数据本身“之前”，先做一项记录工作以防万一。"
  },
  {
    "question": "文档中提到了哪两种主要的机制来实现事务的隔离性（Isolation）？",
    "options": [
      "日志记录 (Logging) 和 回滚操作 (Rollback)",
      "锁机制 (Locking Mechanism) 和 多版本并发控制 (MVCC)",
      "约束检查 (Constraint Checking) 和 触发器 (Triggers)",
      "保存点 (Savepoints) 和 检查点 (Checkpointing)"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档在“隔离性的实现机制”一节中明确列出了锁机制和多版本并发控制（MVCC）作为实现隔离性的主要技术。锁通过阻止并发事务对同一数据的冲突访问来保证隔离，而MVCC则通过为数据维护多个版本来允许读写操作并发执行，提高性能。",
    "source": "文档中「隔离性（Isolation）」->「4. 隔离性的实现机制」部分",
    "hint": "思考一下数据库如何管理多个用户同时读写相同数据，以避免相互干扰。"
  }
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                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  